The present invention relates to forms and components thereof for use in concrete forming and in particular, forms and components thereof which include trusses for forming of concrete floors. The forms preferrably are of the type that are adapted to be lifted by crane between floors of a building during the construction thereof, thereby substantially reducing the time required to set up the form for pouring of the next floor. In particular, the invention is directed to forms which provide additional flexibility and convenient adjustment to define a system for forming of ceilings of different heights or vaulted ceilings.
Flying forms, which are essentially a number of interconnected truss structures adapted to be moved on rollers or the like beyond the building and lifted to the next floor, greatly reduce the required labour necessary for set-up of the forms. Forms of this type include U.S. Pat. Nos. 4,077,172, 3,966,164, and 3,787,020 as but some examples. Recent architectural design to provide additional strength has used concrete ceilings provided with concrete beams which require a stepped ceiling. It is also common to provide a concrete sill at the edge of the floor and a downwardly extending edge portion from the ceiling to reduce the window size. Such structures present additional problems as "packing" is required on the top surface of the truss to accomodate the changing heights of the ceiling. This "packing" is commonly made of wood and beams and as such is very labour intensive and costly. The amount of "packing" can be quite substantial as the top chord of the truss can only be located below the lowest position of the ceiling. When the truss is collapsed for movement between floors, by the lower legs being retracted within the truss, the effective height of the truss is the extent to which the legs may extend below the truss, the height of the truss and the height of any "packing" material secured above the truss. Often this effective height is such that flying forms cannot be used due to the reduced clear area between the concrete sill and downwardly extending ceiling edge.
According to the present invention, a system is provided which uses an intermediate truss which has extendable legs associated therewith. Certain of the legs are associated with the truss to extend below the truss for engaging a support surface and other legs extend above the truss to engage a load collecting beams. Movement of the truss between floors is possible as the lower extension legs collapse or telescope within the truss. The truss is such that the legs each telescope within their own associated tube or recess of the truss whereby the length of the leg can be approximately equal to the height of the truss and, it can be extended further by use of a screw jack. The amount of "packing" and the labour associated therewith is reduced as the extendable legs above the truss are adjusted to accomodate the height of the ceiling and position load collecting beams. As each leg is independently movable within the truss, maximum height of the truss and legs is increased by about the height of the truss as legs extend top and bottom. An upright member for a truss according to an aspect of the invention comprises two paired members disposed in parallel relation and connected to each other by connecting means intermediate the said members. Each of the members includes generally planar opposed parallel bearing surfaces and each bearing surface on one member is colinear with a bearing surface on the other tube member.